Tidal Lagoon - Energy from the Ocean, UK Gov is putting money in it

[dannyf]

That is what happens if there is too much load change beyond the ability of the grid control to compensate.

Something this simple, however, apparently is beyond some people's ability and willingness to comprehend.

How sad.

[mtdoc]

It's true that the current electricity generating structure cannot function without fossil fuel generating plants. In theory, with enough large scale storage (pumped hydro, molten salt?) you could create a functioning, reliable grid based solely on renewables - but reality is different.  Will we ever get there?  No - and here's why:

The current state of the world, economically, technologically, politically is completely dependent on the energy density and portability of fossil fuels. We cannot have business as usual without them - and eventually we won't.  We cannot sustain a world population of 7+ billion without them. And eventually we won't.

And here's the rub - we cannot entirely replace fossil fuels- even just for electricity production - without the excess energy
available to society that they provide. Building solar panels, windmills, tidal generating stations and nuclear plants requires oil - and lots of it - not just for the mining, refining, transportations and manufacturing of the materials required - but also for the capital to be available for the build out. The oil must be cheap for the build out - but also expensive for it to make economic sense for private industry to do it.

We're in an Energy Trap


Fossil fuels are a finite resource and oil, in particular, is the keystone commodity needed to keep the current state of affairs in order. It a complicated set of feedback loops that keeps the current system (including electricity production) afloat.

Conventional oil production has been in a plateau since 2005. Tight oil from the US is entirely responsible for the increase in worldwide production since then. But this oil is costly to extract and has a much lower net energy yield. Shale oil wells have a short lifespan and constant (expensive) new drilling is required just to keep pace. This drilling is financed by cheap debt (thanks to central bankers) which can only be paid back if oil prices stay high.

Without cheap oil the economy can't grow, but without expensive oil production cannot grow and demand stalls or declines. This has led to the current price crash. Production can't decline fast enough to keep pace (debt needs to be paid back!) - but it will and prices may rise again some but will there be the same cheap financing available the next time after the junk bond defaults from this go round?

With each iteration the situation will get more dire.  This is what happens when a finite resource is peaking but because it is happening with oil - THE keystone resource of our current civilization - the impact will be huge.

It's not a matter of if but when. When is impossible to predict. There's an an argument to be made that the current decline in oil prices is a harbinger of a near term collapse due to it's interdependence with the world financial system.  And there's a case to be made that in 2012 a tipping point was reached thermodynamically whereby oil production has gone from an energy source to an energy sink.

Now this is an engineering forum so I'm sure many here will insist that there is a technological solution to this problem. Perhaps there will be - (cold fusion?) I hope there is- but I don't think so. The necessary large scale technological advancement itself depends on the resources of our system as it currently exists. It would require long term thinking and political will - both of which are in short supply.

I don't know when it all falls apart. Maybe not in my lifetime - but certainly within my young children lifetimes. I hope I'm wrong.

That's it for your dally doom and gloom report. Carry on....

[Someone]

This shows that today there will be almost zero wind power generation anywhere in the UK. It will be very little better tomorrow.

And yet... http://www.gridwatch.templar.co.uk/

That's a very interesting resource; thanks; bookmarked.

From that we can see on the 17th we lost 95% of the peak wind power (~300 vs 5869) measured over the past year.
From that we can see on the 17th we lost 82% of the mean wind power (~300 vs 1705) measured over the past year.

Now, what conventional plant would you use to replace that when (not if) it occurs again?

It doesn't have to be replaced with a conventional plant, a plant that can store energy and release it on demand is sufficient. Hydro and Tidal are two such plants that can provide storage of power, along with coal, gas, nuclear, etc.

[Someone]

Intermittent isn't the really big issue with wind. Unpredictability is.

A grid is unique in that at any given time, it is perfectly balanced: supply = demand all the time.

So even if you know for sure that 100MW of power is coming on line at 10am, it is still a huge headache for the grid operator on consuming that additional power.

That's why the base load operators insist on charging solar or wind generators to pull them into the grid. Intermittent power generation has negative value to a grid.

The only reason we are paying them now is driven by policy and not economics.

Its not an effort to absorb 100MW on the UK grid, between the 4 pumped storage installations and the ability to throttle back non pumped hydro several GW can be dispatched in either direction.

[tggzzz]

This shows that today there will be almost zero wind power generation anywhere in the UK. It will be very little better tomorrow.

And yet... http://www.gridwatch.templar.co.uk/

That's a very interesting resource; thanks; bookmarked.

From that we can see on the 17th we lost 95% of the peak wind power (~300 vs 5869) measured over the past year.
From that we can see on the 17th we lost 82% of the mean wind power (~300 vs 1705) measured over the past year.

Now, what conventional plant would you use to replace that when (not if) it occurs again?

It doesn't have to be replaced with a conventional plant, a plant that can store energy and release it on demand is sufficient. Hydro and Tidal are two such plants that can provide storage of power, along with coal, gas, nuclear, etc.

The UK pumped storage is so limited in capacity that it can only be used for two purposes: "black start" emergency reserve and for "load spikes". It cannot, emphatically, be used for peak load nor for long-term storage. I wish the UK's topology was otherwise, because it is a very good mechanism for storing power.

Tidal is much more limited in (at least) two respects. Firstly it is and always will be intermittant. Secondly too many people "double-count" it for generation and for storage, quietly ignoring the disadvantages.

[tggzzz]

Intermittent isn't the really big issue with wind. Unpredictability is.

A grid is unique in that at any given time, it is perfectly balanced: supply = demand all the time.

So even if you know for sure that 100MW of power is coming on line at 10am, it is still a huge headache for the grid operator on consuming that additional power.

That's why the base load operators insist on charging solar or wind generators to pull them into the grid. Intermittent power generation has negative value to a grid.

The only reason we are paying them now is driven by policy and not economics.

Its not an effort to absorb 100MW on the UK grid, between the 4 pumped storage installations and the ability to throttle back non pumped hydro several GW can be dispatched in either direction.

Do the arithmetic, and tell us how long they will at full output capacity and without breaking into the vital "black start" reserve. It isn't as long as most people think.

BTW, one of the things that frightens grid engineers is the requirement that you need electricity to re-start a power station. If too many are knocked offline simultaneously, or cannot connect to those that are online, then there are very serious problems getting any capacity going again. Hence the requirement for the black start reserve.

Yes, such things have occurred several times, particularly in the US, Canada and Hawaii. We were lucky the earth was pointing in the wrong direction (literally) for some of those to happen in the UK.

[Someone]

This shows that today there will be almost zero wind power generation anywhere in the UK. It will be very little better tomorrow.

And yet... http://www.gridwatch.templar.co.uk/

That's a very interesting resource; thanks; bookmarked.

From that we can see on the 17th we lost 95% of the peak wind power (~300 vs 5869) measured over the past year.
From that we can see on the 17th we lost 82% of the mean wind power (~300 vs 1705) measured over the past year.

Now, what conventional plant would you use to replace that when (not if) it occurs again?

It doesn't have to be replaced with a conventional plant, a plant that can store energy and release it on demand is sufficient. Hydro and Tidal are two such plants that can provide storage of power, along with coal, gas, nuclear, etc.

The UK pumped storage is so limited in capacity that it can only be used for two purposes: "black start" emergency reserve and for "load spikes". It cannot, emphatically, be used for peak load nor for long-term storage. I wish the UK's topology was otherwise, because it is a very good mechanism for storing power.

Tidal is much more limited in (at least) two respects. Firstly it is and always will be intermittant. Secondly too many people "double-count" it for generation and for storage, quietly ignoring the disadvantages.

It is currently limited, but you are asking how to increase the dynamic generation capacity by adding more conventional plants, so why not add pumped storage, there are many ways to grow the grid capacity but they are intertwined. It currently has shorter payoff periods than conventional or renewable generation.

[Someone]

Intermittent isn't the really big issue with wind. Unpredictability is.

A grid is unique in that at any given time, it is perfectly balanced: supply = demand all the time.

So even if you know for sure that 100MW of power is coming on line at 10am, it is still a huge headache for the grid operator on consuming that additional power.

That's why the base load operators insist on charging solar or wind generators to pull them into the grid. Intermittent power generation has negative value to a grid.

The only reason we are paying them now is driven by policy and not economics.

Its not an effort to absorb 100MW on the UK grid, between the 4 pumped storage installations and the ability to throttle back non pumped hydro several GW can be dispatched in either direction.

Do the arithmetic, and tell us how long they will at full output capacity and without breaking into the vital "black start" reserve. It isn't as long as most people think.

BTW, one of the things that frightens grid engineers is the requirement that you need electricity to re-start a power station. If too many are knocked offline simultaneously, or cannot connect to those that are online, then there are very serious problems getting any capacity going again. Hence the requirement for the black start reserve.

Yes, such things have occurred several times, particularly in the US, Canada and Hawaii. We were lucky the earth was pointing in the wrong direction (literally) for some of those to happen in the UK.

Any type of plant can be equipped for black start, but the smooth control of hydro is particularly suited to it. With the pumped storage schemes proposed that minimise impact on the natural environment they only plan to utilise the extent of the existing natural water height variation which would leave enormous untapped energy for emergencies. Or just have enough of it that you can keep a reserve on hand at all times, there are no difficult challenges here. Other countries (such as Australia) combine their hydro with drinking water supplies where a minimum level is maintained below which no power is generated.

You were trying to make out that dissipating excess power in the grid is hard, it isn't, pumping hydro and spooling down gas (or feathering wind, or disconnecting solar) can absorb huge swings in the power balance and as more renewables come online the need for storage increases.

[Someone]

This shows that today there will be almost zero wind power generation anywhere in the UK. It will be very little better tomorrow.

And yet... http://www.gridwatch.templar.co.uk/

That's a very interesting resource; thanks; bookmarked.

From that we can see on the 17th we lost 95% of the peak wind power (~300 vs 5869) measured over the past year.
From that we can see on the 17th we lost 82% of the mean wind power (~300 vs 1705) measured over the past year.

Now, what conventional plant would you use to replace that when (not if) it occurs again?

It doesn't have to be replaced with a conventional plant, a plant that can store energy and release it on demand is sufficient. Hydro and Tidal are two such plants that can provide storage of power, along with coal, gas, nuclear, etc.

The UK pumped storage is so limited in capacity that it can only be used for two purposes: "black start" emergency reserve and for "load spikes". It cannot, emphatically, be used for peak load nor for long-term storage. I wish the UK's topology was otherwise, because it is a very good mechanism for storing power.

Tidal is much more limited in (at least) two respects. Firstly it is and always will be intermittant. Secondly too many people "double-count" it for generation and for storage, quietly ignoring the disadvantages.

Tidal power or hydro can generate and store very easily, the energy harvested will be reduced but the peak power and energy available can be increased many times over. There is no intermittency about it when it is run as storage (and the associated small amount of generation) as the power can be delivered at any time of the day or night when planned in advance.

[zapta]

Unfortunately for proponents of nuclear power, the Hollande government has committed to reduce France's nuclear generation to 50% by 2025.

Let me guess, he is a socialist.

[tggzzz]

The UK pumped storage is so limited in capacity that it can only be used for two purposes: "black start" emergency reserve and for "load spikes". It cannot, emphatically, be used for peak load nor for long-term storage. I wish the UK's topology was otherwise, because it is a very good mechanism for storing power.

Tidal is much more limited in (at least) two respects. Firstly it is and always will be intermittant. Secondly too many people "double-count" it for generation and for storage, quietly ignoring the disadvantages.

Tidal power or hydro can generate and store very easily, the energy harvested will be reduced but the peak power and energy available can be increased many times over. There is no intermittency about it when it is run as storage (and the associated small amount of generation) as the power can be delivered at any time of the day or night when planned in advance.

You'll need to explain how you can generate energy when the water level is the same on both sides of the barrage.

Bear in mind that at least twice a day I look at the tide level associated with the Severn, and hence a Severn or Swansea barrage. I viscerally *know* what the tides do. I get the strong feeling that many people's understanding of tides is from books or holidays by the open sea.

Q1 When the tide is high, how much surplus power from intermittent sources could be stored?
A1 Zero
A2 A tiny amount, provided you are prepared to flood Bristol (or presumably Swansea) city centre. That very very nearly happens naturally; I have watched buildings underwater twice in 25 years. For last year's event, search for "bristol flood", or see http://www.westerndailypress.co.uk/images/localworld/ugc-images/276309/Article/images/20404985/5683047-large.jpg or http://www.bathchronicle.co.uk/images/localworld/ugc-images/276329/Article/images/20396461/5676879-large.jpg

Q2 The tide is low, so surplus energy can be stored. Twelve hours later, how much extra energy is available as a result of that storage?
A1: zero. All that you managed to achieve was filling up the basin a little earlier than would have occurred naturally when the tide came in. And in doing that you would have lost the energy that could have been extracted from the incoming tide.

[tggzzz]

This shows that today there will be almost zero wind power generation anywhere in the UK. It will be very little better tomorrow.

And yet... http://www.gridwatch.templar.co.uk/

That's a very interesting resource; thanks; bookmarked.

From that we can see on the 17th we lost 95% of the peak wind power (~300 vs 5869) measured over the past year.
From that we can see on the 17th we lost 82% of the mean wind power (~300 vs 1705) measured over the past year.

Now, what conventional plant would you use to replace that when (not if) it occurs again?

It doesn't have to be replaced with a conventional plant, a plant that can store energy and release it on demand is sufficient. Hydro and Tidal are two such plants that can provide storage of power, along with coal, gas, nuclear, etc.

The UK pumped storage is so limited in capacity that it can only be used for two purposes: "black start" emergency reserve and for "load spikes". It cannot, emphatically, be used for peak load nor for long-term storage. I wish the UK's topology was otherwise, because it is a very good mechanism for storing power.

Tidal is much more limited in (at least) two respects. Firstly it is and always will be intermittant. Secondly too many people "double-count" it for generation and for storage, quietly ignoring the disadvantages.

It is currently limited, but you are asking how to increase the dynamic generation capacity by adding more conventional plants,

I'm not asking that at all. Plaese don't make strawman arguments.

The people that want us to unduly rely on intermittent sources are the ones that require dynamic capability - even thought they are loathe to admit it.

so why not add pumped storage,

Where in the UK? Seriously. If you have a good solid answer then you also know where there are serious amounts of money to be made - and I suggest you personally get in on the act.

In the UK there are only a small number of sites available, and it is pretty well exploited. It is probably different in other countries, but this thread is monimally about the Swansea barrage.

It currently has shorter payoff periods than conventional or renewable generation.

Economics are a separate issue, and one that merely obfuscates the fundamental physics. I have not discussed the economics.

[tggzzz]

Do the arithmetic, and tell us how long they will at full output capacity and without breaking into the vital "black start" reserve. It isn't as long as most people think.

BTW, one of the things that frightens grid engineers is the requirement that you need electricity to re-start a power station. If too many are knocked offline simultaneously, or cannot connect to those that are online, then there are very serious problems getting any capacity going again. Hence the requirement for the black start reserve.

Yes, such things have occurred several times, particularly in the US, Canada and Hawaii. We were lucky the earth was pointing in the wrong direction (literally) for some of those to happen in the UK.

Any type of plant can be equipped for black start, but the smooth control of hydro is particularly suited to it. With the pumped storage schemes proposed that minimise impact on the natural environment they only plan to utilise the extent of the existing natural water height variation which would leave enormous untapped energy for emergencies. Or just have enough of it that you can keep a reserve on hand at all times, there are no difficult challenges here. Other countries (such as Australia) combine their hydro with drinking water supplies where a minimum level is maintained below which no power is generated.

Pumped storage or hydro has other unique significant advantages w.r.t. black start reserve. Ask grid engineers. Tidal also has similar advantages, but to a lesser extent.

You were trying to make out that dissipating excess power in the grid is hard, it isn't,

Please show where I have argued that. Please stop incorrectly putting words into other people's mouths. Please stop making strawman arguments. You do a disservice to yourself and your arguments.

pumping hydro and spooling down gas (or feathering wind, or disconnecting solar) can absorb huge swings in the power balance and as more renewables come online the need for storage increases.

Rubbish. Since you use the word "huge", please read the universally acclaimed book at http:www.withouthotair.com which the author wrote to replace adjectives with numbers:

The trouble with this sort of language is that it’s not
suf?cient to know that something is huge: we need to know how the one
“huge” compares with another “huge,” namely our huge energy consump-
tion. To make this comparison, we need numbers, not adjectives.

[Someone]

The UK pumped storage is so limited in capacity that it can only be used for two purposes: "black start" emergency reserve and for "load spikes". It cannot, emphatically, be used for peak load nor for long-term storage. I wish the UK's topology was otherwise, because it is a very good mechanism for storing power.

Tidal is much more limited in (at least) two respects. Firstly it is and always will be intermittant. Secondly too many people "double-count" it for generation and for storage, quietly ignoring the disadvantages.

Tidal power or hydro can generate and store very easily, the energy harvested will be reduced but the peak power and energy available can be increased many times over. There is no intermittency about it when it is run as storage (and the associated small amount of generation) as the power can be delivered at any time of the day or night when planned in advance.

You'll need to explain how you can generate energy when the water level is the same on both sides of the barrage.

Bear in mind that at least twice a day I look at the tide level associated with the Severn, and hence a Severn or Swansea barrage. I viscerally *know* what the tides do. I get the strong feeling that many people's understanding of tides is from books or holidays by the open sea.

Q1 When the tide is high, how much surplus power from intermittent sources could be stored?
A1 Zero
A2 A tiny amount, provided you are prepared to flood Bristol (or presumably Swansea) city centre. That very very nearly happens naturally; I have watched buildings underwater twice in 25 years. For last year's event, search for "bristol flood", or see http://www.westerndailypress.co.uk/images/localworld/ugc-images/276309/Article/images/20404985/5683047-large.jpg or http://www.bathchronicle.co.uk/images/localworld/ugc-images/276329/Article/images/20396461/5676879-large.jpg

Q2 The tide is low, so surplus energy can be stored. Twelve hours later, how much extra energy is available as a result of that storage?
A1: zero. All that you managed to achieve was filling up the basin a little earlier than would have occurred naturally when the tide came in. And in doing that you would have lost the energy that could have been extracted from the incoming tide.

Q1, some quantity of energy can be stored at any time if it is going to be released at a specific (and known) time in the future even at high tide in certain circumstances you might have an incentive to pump water OUT of the basin. When to produce and when to store is based on the predicted fluctuations of the market so you don't always want to harvest all the power in the tide if the storage capacity could make more money later. But you know all this and are just trolling.

Q2, round trip efficiency is around 80% or higher for pumped storage. You wouldn't buy energy and store it if you weren't planning on using it so keeping it through the next high tide would be stupid.

Its possible to come up with all sorts of uneconomical ways to operate any plant, you could burn an open cycle gas plant all night when the market power price is at its cheapest and turn a loss too.

[Someone]

You were trying to make out that dissipating excess power in the grid is hard, it isn't,

Please show where I have argued that. Please stop incorrectly putting words into other people's mouths. Please stop making strawman arguments. You do a disservice to yourself and your arguments.

Apologies, got confused with that other person distracting the discussion with straight out lies. But you still challenged my reasoned response to those ridiculous claims with diversions into capacity which is a completely different issue. The existing capacity is not stretched by absorbing transients while other plants are brought up/down. Move to more renewables and there will be a need for more storage capacity.

You were trying to make out that dissipating excess power in the grid is hard, it isn't,

Please show where I have argued that. Please stop incorrectly putting words into other people's mouths. Please stop making strawman arguments. You do a disservice to yourself and your arguments.

Apologies for the same collision, but I'm making the strawman? you need to check how that works when I address the original post and you come in with tangents.

[Someone]

pumping hydro and spooling down gas (or feathering wind, or disconnecting solar) can absorb huge swings in the power balance and as more renewables come online the need for storage increases.

Rubbish. Since you use the word "huge", please read the universally acclaimed book at http:www.withouthotair.com which the author wrote to replace adjectives with numbers:

The trouble with this sort of language is that it’s not
suf?cient to know that something is huge: we need to know how the one
“huge” compares with another “huge,” namely our huge energy consump-
tion. To make this comparison, we need numbers, not adjectives.

You might want to read that book yourself, it is indeed a well balanced and in depth look at energy in the UK, I was so impressed with the work I have conversed with the author and shared some topical data with him. But as to the specifics of describing the grids ability to absorb fluctuations I had already put a number on the figure and reinforced it with colourful language, if you'd like to come up with a more accurate measure than several GW for the peak pumping capacity available in the UK it would be welcome. Losing power from the grid is easy, the slew rate of the largest thermal plants being the limiting factor but that can be partially absorbed with pumped storage. The discussion was on absorbing additional power and you wander off into the specifics of current storage capacity in pumped hydro.

so why not add pumped storage,

Where in the UK? Seriously. If you have a good solid answer then you also know where there are serious amounts of money to be made - and I suggest you personally get in on the act.

Sustainable Energy - Without the Hot Air should have educated you on that issue, discussing the alternate locations considered when Dinorwig was constructed and then going on to suggest an easily accessible 100GWh up to 400GWh just in existing conventional water catchments in Scotland only. If you look to the published literature on pumped storage it is found to be economically viable in surprisingly small installations even in less than ideal sitings, and entirely man made reservoirs are also profitable, so there is significantly more storage possible that is not encompassed in that estimate.

[tggzzz]

The UK pumped storage is so limited in capacity that it can only be used for two purposes: "black start" emergency reserve and for "load spikes". It cannot, emphatically, be used for peak load nor for long-term storage. I wish the UK's topology was otherwise, because it is a very good mechanism for storing power.

Tidal is much more limited in (at least) two respects. Firstly it is and always will be intermittant. Secondly too many people "double-count" it for generation and for storage, quietly ignoring the disadvantages.

Tidal power or hydro can generate and store very easily, the energy harvested will be reduced but the peak power and energy available can be increased many times over. There is no intermittency about it when it is run as storage (and the associated small amount of generation) as the power can be delivered at any time of the day or night when planned in advance.

You'll need to explain how you can generate energy when the water level is the same on both sides of the barrage.

Bear in mind that at least twice a day I look at the tide level associated with the Severn, and hence a Severn or Swansea barrage. I viscerally *know* what the tides do. I get the strong feeling that many people's understanding of tides is from books or holidays by the open sea.

Q1 When the tide is high, how much surplus power from intermittent sources could be stored?
A1 Zero
A2 A tiny amount, provided you are prepared to flood Bristol (or presumably Swansea) city centre. That very very nearly happens naturally; I have watched buildings underwater twice in 25 years. For last year's event, search for "bristol flood", or see http://www.westerndailypress.co.uk/images/localworld/ugc-images/276309/Article/images/20404985/5683047-large.jpg or http://www.bathchronicle.co.uk/images/localworld/ugc-images/276329/Article/images/20396461/5676879-large.jpg

Q2 The tide is low, so surplus energy can be stored. Twelve hours later, how much extra energy is available as a result of that storage?
A1: zero. All that you managed to achieve was filling up the basin a little earlier than would have occurred naturally when the tide came in. And in doing that you would have lost the energy that could have been extracted from the incoming tide.

Q1, some quantity of energy can be stored at any time if it is going to be released at a specific (and known) time in the future even at high tide in certain circumstances you might have an incentive to pump water OUT of the basin. When to produce and when to store is based on the predicted fluctuations of the market so you don't always want to harvest all the power in the tide if the storage capacity could make more money later. But you know all this and are just trolling.

Not in the Severn without flooding Bristol city centre. That's not trolling. The pictures illustrate the extreme of a >14m high tide, but it is within 1m of that most months - have a look at the tide tables.

Q2, round trip efficiency is around 80% or higher for pumped storage. You wouldn't buy energy and store it if you weren't planning on using it so keeping it through the next high tide would be stupid.

First sentence is true but irrelevant. In the UK if we are to rely on intermittents as some wishful-thinkers propose, we either have to store energy for several days (not hours). I chose that question carefully to represent real conditions. The alternative os to have the equivalent conventional plant capacity standing idle and then being thermally cycled.

[tggzzz]

You were trying to make out that dissipating excess power in the grid is hard, it isn't,

Please show where I have argued that. Please stop incorrectly putting words into other people's mouths. Please stop making strawman arguments. You do a disservice to yourself and your arguments.

Apologies, got confused with that other person distracting the discussion with straight out lies. But you still challenged my reasoned response to those ridiculous claims with diversions into capacity which is a completely different issue. The existing capacity is not stretched by absorbing transients while other plants are brought up/down. Move to more renewables and there will be a need for more storage capacity.

Apologies accepted; it happens.

But, again, I haven't made those claims you are ascribing to me.

[Mechanical Menace]

Unfortunately for proponents of nuclear power, the Hollande government has committed to reduce France's nuclear generation to 50% by 2025.

Let me guess, he is a socialist.

Yeah, but TBH French politics have extremes in the "mainstream" we really don't. Even the craziest of the Democrats (or Labour here) would think their left wingers go way too far and even the craziest Republicans (or Conservatives and UKIP here) would think their right wingers shouldn't be saying that in public

[Someone]

The UK pumped storage is so limited in capacity that it can only be used for two purposes: "black start" emergency reserve and for "load spikes". It cannot, emphatically, be used for peak load nor for long-term storage. I wish the UK's topology was otherwise, because it is a very good mechanism for storing power.

Tidal is much more limited in (at least) two respects. Firstly it is and always will be intermittant. Secondly too many people "double-count" it for generation and for storage, quietly ignoring the disadvantages.

Tidal power or hydro can generate and store very easily, the energy harvested will be reduced but the peak power and energy available can be increased many times over. There is no intermittency about it when it is run as storage (and the associated small amount of generation) as the power can be delivered at any time of the day or night when planned in advance.

You'll need to explain how you can generate energy when the water level is the same on both sides of the barrage.

Bear in mind that at least twice a day I look at the tide level associated with the Severn, and hence a Severn or Swansea barrage. I viscerally *know* what the tides do. I get the strong feeling that many people's understanding of tides is from books or holidays by the open sea.

Q1 When the tide is high, how much surplus power from intermittent sources could be stored?
A1 Zero
A2 A tiny amount, provided you are prepared to flood Bristol (or presumably Swansea) city centre. That very very nearly happens naturally; I have watched buildings underwater twice in 25 years. For last year's event, search for "bristol flood", or see http://www.westerndailypress.co.uk/images/localworld/ugc-images/276309/Article/images/20404985/5683047-large.jpg or http://www.bathchronicle.co.uk/images/localworld/ugc-images/276329/Article/images/20396461/5676879-large.jpg

Q2 The tide is low, so surplus energy can be stored. Twelve hours later, how much extra energy is available as a result of that storage?
A1: zero. All that you managed to achieve was filling up the basin a little earlier than would have occurred naturally when the tide came in. And in doing that you would have lost the energy that could have been extracted from the incoming tide.

Q1, some quantity of energy can be stored at any time if it is going to be released at a specific (and known) time in the future even at high tide in certain circumstances you might have an incentive to pump water OUT of the basin. When to produce and when to store is based on the predicted fluctuations of the market so you don't always want to harvest all the power in the tide if the storage capacity could make more money later. But you know all this and are just trolling.

Not in the Severn without flooding Bristol city centre. That's not trolling. The pictures illustrate the extreme of a >14m high tide, but it is within 1m of that most months - have a look at the tide tables.

Q2, round trip efficiency is around 80% or higher for pumped storage. You wouldn't buy energy and store it if you weren't planning on using it so keeping it through the next high tide would be stupid.

First sentence is true but irrelevant. In the UK if we are to rely on intermittents as some wishful-thinkers propose, we either have to store energy for several days (not hours). I chose that question carefully to represent real conditions. The alternative os to have the equivalent conventional plant capacity standing idle and then being thermally cycled.

You clearly aren't the person to operate such a tidal plant, pumping water OUT of the stored basin of the hypothetical Severn barrage should avoid flooding Bristol.

All sorts of specific situations can be dreamt up that make it seem illogical or silly but when operated in sympathy with the grid tidal storage can be a useful short term storage, and/or it can generate some power. If there was a known excess of cheap power you would not be stuck with zero storage, and tidal plants without elevated storage are of course illogical to carry storage through multiple tides.

[tggzzz]

The UK pumped storage is so limited in capacity that it can only be used for two purposes: "black start" emergency reserve and for "load spikes". It cannot, emphatically, be used for peak load nor for long-term storage. I wish the UK's topology was otherwise, because it is a very good mechanism for storing power.

Tidal is much more limited in (at least) two respects. Firstly it is and always will be intermittant. Secondly too many people "double-count" it for generation and for storage, quietly ignoring the disadvantages.

Tidal power or hydro can generate and store very easily, the energy harvested will be reduced but the peak power and energy available can be increased many times over. There is no intermittency about it when it is run as storage (and the associated small amount of generation) as the power can be delivered at any time of the day or night when planned in advance.

You'll need to explain how you can generate energy when the water level is the same on both sides of the barrage.

Bear in mind that at least twice a day I look at the tide level associated with the Severn, and hence a Severn or Swansea barrage. I viscerally *know* what the tides do. I get the strong feeling that many people's understanding of tides is from books or holidays by the open sea.

Q1 When the tide is high, how much surplus power from intermittent sources could be stored?
A1 Zero
A2 A tiny amount, provided you are prepared to flood Bristol (or presumably Swansea) city centre. That very very nearly happens naturally; I have watched buildings underwater twice in 25 years. For last year's event, search for "bristol flood", or see http://www.westerndailypress.co.uk/images/localworld/ugc-images/276309/Article/images/20404985/5683047-large.jpg or http://www.bathchronicle.co.uk/images/localworld/ugc-images/276329/Article/images/20396461/5676879-large.jpg

Q2 The tide is low, so surplus energy can be stored. Twelve hours later, how much extra energy is available as a result of that storage?
A1: zero. All that you managed to achieve was filling up the basin a little earlier than would have occurred naturally when the tide came in. And in doing that you would have lost the energy that could have been extracted from the incoming tide.

Q1, some quantity of energy can be stored at any time if it is going to be released at a specific (and known) time in the future even at high tide in certain circumstances you might have an incentive to pump water OUT of the basin. When to produce and when to store is based on the predicted fluctuations of the market so you don't always want to harvest all the power in the tide if the storage capacity could make more money later. But you know all this and are just trolling.

Not in the Severn without flooding Bristol city centre. That's not trolling. The pictures illustrate the extreme of a >14m high tide, but it is within 1m of that most months - have a look at the tide tables.

Q2, round trip efficiency is around 80% or higher for pumped storage. You wouldn't buy energy and store it if you weren't planning on using it so keeping it through the next high tide would be stupid.

First sentence is true but irrelevant. In the UK if we are to rely on intermittents as some wishful-thinkers propose, we either have to store energy for several days (not hours). I chose that question carefully to represent real conditions. The alternative os to have the equivalent conventional plant capacity standing idle and then being thermally cycled.

You clearly aren't the person to operate such a tidal plant, pumping water OUT of the stored basin of the hypothetical Severn barrage should avoid flooding Bristol.

All sorts of specific situations can be dreamt up that make it seem illogical or silly but when operated in sympathy with the grid tidal storage can be a useful short term storage, and/or it can generate some power. If there was a known excess of cheap power you would not be stuck with zero storage, and tidal plants without elevated storage are of course illogical to carry storage through multiple tides.

If you pump it out at high tide, which you would have to do in the Severn, the subject of this thread, then not only have you not stored energy you have actually "wasted" it.

You appear to be very reluctant to answer the question I asked about the Severn, in the UK, with UK constraints. Other locations will have different constraints and your suggestions might be relevant there - but they are not in the Severn.

[Someone]

If you pump it out at high tide, which you would have to do in the Severn, the subject of this thread, then not only have you not stored energy you have actually "wasted" it.

You appear to be very reluctant to answer the question I asked about the Severn, in the UK, with UK constraints. Other locations will have different constraints and your suggestions might be relevant there - but they are not in the Severn.

Which question have I not answered? You predicate that sorting energy in a hypothetical Severn Barrage basin at high tide will flood Bristol, there are two problems with this:

It assumes that every high tide is high enough to be just on the point that any more water height will flood Bristol. Tide peaks vary, so there will some times be additional storage available even at high tide when the basin is being filled in anticipation of demand more than 2-3 hours away.

Which is the second part that if it is planned to generate in the time up to 2-3 hours after the high tide then the basin is ideally empty at the high tide. Further emptying it, perhaps even below the low tide, or even below the record low tide depth can store energy for release in the following several hours.

These patterns of energy delivery are true of any pumped tidal plant, its not a simple decision to produce power or not as it is with elevated storage hydro, some planning is needed to have the two sides of the barrage in the right balance for the predicted generation.

Economics are a separate issue, and one that merely obfuscates the fundamental physics. I have not discussed the economics.

Its all about economics, the above examples I'm providing are assuming the tidal plant operator only has access to their storage capacity and wishes to maximise their profit. If the same operator had access to sufficient conventional pumped hydro they would likely be running the tidal plant to maximise energy harvesting efficiency and using the pumped hydro to deliver that energy when its most cost effective.

If you want to discuss the possible flooding of Bristol with regard to a Severn Barrage, then it is in fact able to protect them from flooding events. All off a sudden there is a huge economic value in having control of the basin depth.

[tggzzz]

Only half and hour until the eclipse and all of Europe's energy grid implodes due to the massive amount of solar PV we have 

Stop trolling.

It won't implode because there is sufficient conventional capacity to cover for its absence - and long may that continue.

[tom66]

Hmm. From what I heard, European grid operators had been planning for this event and were able to cover the shortfall of about 5GW with conventional power plant generation. The great thing is you can plan for eclipses hundreds of years in advance. Cloud cover is hard to predict more than a week ahead.

[tggzzz]

Apparently we can cope with intermittent sources of energy.

Of course we can - if and only if there are sufficient alternative sources available when needed.

Maybe a tidal lagoon isn't such a crazy idea after all.

All technologies have their limitations. The only crazy thing is to attempt to pretend they don't have limitations.

For intermittent sources you either have to be able to store electricity (or the equivalent), or to have sufficient excess capacity to make up the shortfall.

In the UK the practical storage capacity that is available all the time is, unfortunately, very limited. Fame and riches await the person that invents and creates practical storage technology.